JP5018502B2 - Superconducting cable - Google Patents

Description

  The present invention relates to a superconducting cable mainly composed of a superconducting thin film wire, comprising a superconducting conductor layer or a superconducting shield layer formed by including a superconducting thin film wire with a different superconducting wire, and in particular, having a critical current density versus temperature characteristic. The present invention relates to a stabilized superconducting cable.

  As a superconducting wire, a Bi-based superconducting tape wire (BSCCO (trade name)) typified by a Bi-Sr-Ca-Cu-O tape wire is being put into practical use. This Bi-based superconducting tape wire is a tape wire having a structure in which a plurality of superconducting filaments made of, for example, a Bi2223 phase are embedded in a stabilizing material such as silver. For example, as shown in FIG. 3, the cross section is formed in a tape shape by covering a large number of superconducting filaments 21a made of a bismuth-based oxide superconductor with a metal sheath (metal stabilizing material) 21b made of silver or the like. . As will be described later, such a Bi-based superconducting tape wire 21 has a small change rate of critical current (critical current density (Jc)) with respect to temperature change at around 77K, which is the boiling point of liquid nitrogen, and has a critical temperature as well. Although it has the feature of being high, there is a difficulty in that a large increase in critical current (critical current density (Jc)) cannot be expected even if the refrigerant temperature is lowered.

On the other hand, as a next-generation superconducting wire, development of a Y-based superconducting thin film wire (YBCO), which is a so-called superconducting thin film wire, is in progress (for example, Patent Document 1). The configuration of the Y-based superconducting thin film wire is shown in FIG. The Y-based superconducting thin film wire 11 is formed by sequentially laminating an intermediate layer 13, a superconducting thin film 14, and a protective layer 15 on a tape-like metal substrate 12. As a specific example, Hastelloy (registered trademark) is used as the metal substrate 12, YSZ is used as the intermediate layer 13, a Y-based 123 (YBa ₂ Cu ₃ Oy) thin film is used as the superconducting thin film 14, and silver is used as the protective layer 15. Usually, the intermediate layer 13 and the superconducting thin film 14 are formed only on one side of the metal substrate 12 by laser vapor deposition or the like. As described later, the Y-based superconducting thin film wire 11 has a large rate of change of critical current (critical current density (Jc)) with respect to temperature change at around 77K. Although it has the feature that the current (critical current density (Jc)) rises greatly, there is a drawback that the critical current (critical current density (Jc)) decreases greatly when the operating temperature rises.

  As shown in FIG. 5, for example, a considerably clear difference is recognized in the critical current density (Jc) versus temperature characteristics of the Y-based superconducting thin film wire and the Bi-based superconducting tape wire. That is, at 65 K to 77 K (boiling point of liquid nitrogen) near the operating temperature of the superconducting cable, the Y-based superconducting thin film wire indicated by the alternate long and short dash line is more resistant to the temperature rise than the Bi-based superconducting tape wire indicated by the two-dot chain line. The decrease in critical current density (Jc) is quite large, and there is a clear difference between the temperature gradients of the critical current density curves of both wires.

Due to the difference in the critical current density (Jc) vs. temperature characteristics of both wires, there is a large difference in the temperature rise that can be instantaneously restored when a large current flows temporarily during a short-circuit accident. It is done. Normally, when a large short-circuit current flows in the transmission line system, the cable is disconnected from the line after a predetermined time determined by the specifications of the circuit breaker, but the cable is caused by the short-circuit current flowing in the superconducting cable before it is disconnected. Temperature rises. Instantaneous recovery refers to a state in which operation is resumed immediately after the accident is removed without causing the superconducting cable to transition to normal conduction even when such a large current flows. The Y-based superconducting thin film wire has a smaller allowable temperature rise that enables instantaneous recovery than the Bi-based superconducting tape wire. The allowable temperature increase range refers to the temperature increase range from the set temperature of the refrigerant during operation to the maximum temperature that can be instantaneously restored.

Conventionally, when a superconducting cable for AC, for example, is constituted by such a Bi-based superconducting tape wire or Y-based superconducting thin film wire, the superconducting conductor layer and the superconducting shield layer are made of Bi-based superconducting tape wire or Y-based superconducting thin-film wire. It was comprised only with any one type of wire. That is, in the Bi-based superconducting cable, the superconducting conductor layer and the superconducting shield layer are formed only by the Bi-based superconducting tape wire (see, for example, Patent Document 2). Further, in a Y-based superconducting cable, a superconducting conductor layer and a superconducting shield layer are formed only by a Y-based superconducting thin film wire (see, for example, Patent Document 3).
JP 2001-31418 JP 2006-331893 JP JP 2007-188844

  Y-based superconducting cable has a smaller temperature range from the operating temperature to the normal conducting transition than Bi-based superconducting cable, so quenching is likely to occur due to heat generation at the intermediate joint part and terminal connection part of the transmission line system. . In addition, the allowable temperature rise that enables instantaneous recovery with respect to the short-circuit current is small, and even when the instantaneous recovery does not occur, the time required for recovery becomes longer. Therefore, in the Y-based superconducting cable, a countermeasure for ensuring the stability of the system has been desired.

  This invention is made | formed in view of such a situation, and it aims at providing the superconducting cable which stabilized the temperature characteristic with respect to a critical current density.

The present invention is a superconducting cable comprising a superconducting conductor layer and a superconducting shield layer,
The superconducting conductor layer is formed of a superconducting thin film wire including a different kind of superconducting wire, and the superconducting wire is formed of a Bi-based superconducting tape wire.

  According to such a configuration, the difficulty of the Y-based superconducting thin film wire that the reduction rate of the critical current density (Jc) when the operating temperature rises is large can be compensated by the Bi-based superconducting tape wire. That is, since the superconducting conductor layer contains Bi-based superconducting tape wire, the characteristic of Bi-based superconducting tape wire that the rate of decrease in critical current density (Jc) when the operating temperature is increased is added to the superconducting conductor layer. be able to. This makes it possible to reduce the decrease rate of the critical current density (Jc) when the operating temperature rises for the entire superconducting conductor layer, and to improve the temperature characteristics of the critical current density (Jc) in the superconducting conductor layer. Can do.

  The Bi-based superconducting tape wire may be disposed in a layer inside the superconducting conductor layer. Since the external parallel magnetic field of the superconducting conductor layer increases as the outer layer increases, by arranging the Bi-based superconducting tape wire on the inner layer of the superconducting conductor layer, the AC current with respect to the external parallel magnetic field is reduced, and the critical current for the external parallel magnetic field is reduced. A superconducting thin film wire with little decrease can be arranged on the outer layer side. Therefore, as a whole, a superconducting conductor layer with a low AC loss and a large capacity can be formed. For example, a Y-based superconducting thin film wire can be used as the superconducting thin film wire.

Another invention is a superconducting cable including a superconducting conductor layer and a superconducting shield layer,
The superconducting shield layer is formed of a superconducting thin film wire including a different kind of superconducting wire, and the superconducting wire is formed of a Bi-based superconducting tape wire.

  According to such a configuration, the difficulty of the Y-based superconducting thin film wire that the reduction rate of the critical current density (Jc) when the operating temperature rises is large can be compensated by the Bi-based superconducting tape wire. That is, since the superconducting shield layer contains Bi-based superconducting tape wire, the characteristic of Bi-based superconducting tape wire that the rate of decrease in critical current density (Jc) when the operating temperature is increased is added to the superconducting shield layer. Can do. As a result, the reduction rate of the critical current density (Jc) when the operating temperature rises can be reduced as a whole of the superconducting shield layer, and the temperature characteristics of the critical current density (Jc) in the superconducting shield layer can be improved. Can do.

  The Bi-based superconducting tape wire may be disposed on the outer layer of the superconducting shield layer. The superconducting shield layer has a larger external parallel magnetic field as the inner layer. Therefore, by arranging the Bi-based superconducting tape wire on the outer layer of the superconducting shield layer, the AC current loss with respect to the external parallel magnetic field is reduced and the critical current with respect to the external parallel magnetic field is reduced. A superconducting thin film wire with little decrease can be arranged on the inner layer side. Therefore, as a whole, a superconducting shield layer having a small amount of AC loss and a large capacity can be formed. For example, a Y-based superconducting thin film wire can be used as the superconducting thin film wire.

  In the superconducting cable of the present invention, since at least one of the superconducting conductor layers is formed of a Bi-based superconducting tape wire, the critical current density (Jc) with respect to temperature characteristics in the superconducting conductor layer is improved, and the instantaneous current against the accident current is improved. It is possible to construct a transmission line system in which the allowable temperature rise that can be restored is expanded.

  In another superconducting cable of the present invention, since at least one of the superconducting shield layers is formed of a Bi-based superconducting tape wire, the critical current density (Jc) with respect to temperature characteristics in the superconducting shield layer is improved, and the accident current is reduced. Thus, it is possible to construct a transmission line system in which the allowable temperature rise that can be instantaneously recovered is expanded.

  Hereinafter, a superconducting cable according to an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a perspective view showing a main configuration of a cable core of a superconducting cable. This cable core includes a former 1, a superconducting conductor layer 2, an insulating layer 3, and a superconducting shield layer 4 in order from the center. The former 1 is formed of a stranded wire or a hollow pipe formed by twisting strands made of a normal conducting material such as Cu, and the insulating layer 3 is formed of kraft paper or composite paper obtained by laminating kraft paper and a polyolefin film. The The superconducting conductor layer 2 includes, for example, an inner layer formed of a Bi-based superconducting tape wire 21 as shown in FIG. 3, and an intermediate layer and an outer layer formed of a Y-based superconducting thin film wire 11. . Superconducting shield layer 4 includes an inner layer formed of Y-based superconducting thin film wire 11 and an outer layer formed of Bi-based superconducting tape wire 21.

  In the superconducting conductor layer 2 in the superconducting cable having such a cable core, the outer parallel magnetic field becomes larger in the outer layer, so that the intermediate layer and the outer layer have less AC loss with respect to the external parallel magnetic field, and the critical current ( The Y-type superconducting thin film wire 11 has a small decrease in Ic). And the inner layer (for example, 1-2 layers by the number of layers) is formed with the Bi type superconducting tape wire 21 in which the critical current density (Jc) decreases little with respect to the temperature rise. With such a configuration, the critical current density (Jc) versus temperature characteristics in the superconducting conductor layer 2 while taking advantage of the characteristics of the Y-based superconducting thin film wire 11 that is excellent in the magnetic field characteristics with little decrease in the critical current (Ic) due to the magnetic field. And a large capacity can be secured by reducing AC loss.

  In the superconducting shield layer 4, the inner parallel layer has a larger external parallel magnetic field. Therefore, the inner layer of the Y-type superconducting thin film wire 11 has less AC loss with respect to the external parallel magnetic field and less critical current (Ic) with respect to the external parallel magnetic field. It is formed with. The outer layer is formed of a Bi-based superconducting tape wire 21 in which the critical current density (Jc) decreases little with increasing temperature. With such a configuration, a critical current density (Jc) pair in the superconducting shield layer 4 is utilized while taking advantage of the characteristics of the Y-based superconducting thin film wire 11 that has a small decrease in critical current (Ic) due to an external parallel magnetic field and is excellent in magnetic field characteristics. The temperature characteristics can be improved, and a large capacity can be secured by reducing AC loss.

  Therefore, when a power transmission line system is constituted by a superconducting cable including the superconducting conductor layer 2 and the superconducting shield layer 4 mixed with the Bi-based superconducting tape wire as described above, a temperature region in which an instantaneous return to an accident current is possible. Is also expanded. Further, even when the instantaneous return is not permitted and the power transmission is stopped (shutdown), the time required for cooling to restart the operation is shortened.

  The temperature characteristics of such a superconducting cable can be confirmed by comparing the temperature characteristics of the critical current density (Jc) of the Bi-based superconducting tape wire and the Y-based superconducting thin film wire with reference to the graph of FIG. In FIG. 2, the horizontal axis represents the temperature of the refrigerant (absolute temperature K), the vertical axis represents the critical current density (Jc) of the Y-based superconducting thin film wire and Bi-based superconducting tape wire, and the value at the boiling point of the refrigerant 77K is the reference value. (= 1.0) is displayed as a ratio to the reference value. As shown in the figure, it can be seen that the slope of the critical current density curve of the Y-based superconducting thin film wire is considerably larger than that of the Bi-based superconducting tape wire at around 77K. That is, in the Y-based superconducting thin film wire, when the refrigerant temperature is lowered, the critical current density (Jc) increases greatly, and the rate of change of the critical current density (Jc) with respect to the temperature change is large. Therefore, the critical current density (Jc) can be greatly increased by lowering the refrigerant temperature, but on the other hand, the critical current density (Jc) decreases greatly when the operating temperature rises. Allowable temperature rise is also small. On the other hand, Bi-based superconducting tape wire has a low rate of decrease in critical current density (Jc) when the operating temperature rises, and the critical temperature is also high. The temperature rise is large.

  For example, in a power transmission line system, if a large current temporarily flows in the superconducting cable due to a short circuit accident or the like, the temperature of the superconducting cable will rise, but if the rise is within the temperature range where normal conduction transition does not occur Instantaneous recovery is possible, and power transmission can be continued while maintaining the superconducting state continuously. In a conventional Y-based superconducting cable in which a superconducting layer is formed only with a Y-based superconducting thin film wire, the allowable temperature rise that enables instantaneous recovery is small, and thus there are many cases where power transmission is stopped. On the other hand, the Bi-based superconducting cable in which the superconducting layer is formed only with the conventional Bi-based superconducting tape wire has a relatively large allowable temperature rise that enables instantaneous recovery, so that the power transmission is stopped more than the Y-based superconducting cable. There will be fewer cases.

  In order to ensure an allowable temperature increase range equivalent to that of a Bi superconducting cable in a transmission line system constructed with a Y superconducting cable, the load factor must be reduced by increasing the amount of wire. However, if such measures are taken, the characteristics of the superconducting cable, which is compact and high-density power transmission, are lost, and the cost of the cable also increases. Therefore, in the superconducting cable of the present invention, the superconducting conductor layer 2 and the superconducting shield layer 4 are combined with the Bi-based superconducting tape wire 21 having a small reduction rate of the critical current density (Jc) when the operating temperature rises. By utilizing the characteristics of the Y-based superconducting thin film wire 11, it is possible to improve the temperature characteristics of the critical current density (Jc) and to construct a transmission line system with a large allowable temperature rise that can be instantaneously restored to the accident current I am doing so. It should be noted that the present invention is not limited to the embodiment, and can be freely improved, changed, etc. as necessary without departing from the gist of the invention.

  Since the superconducting cable of the present invention has a stabilized temperature characteristic of critical current density (Jc), it can be suitably used for construction of a transmission line system that requires stabilization of the system and increase in capacity.

It is a perspective view which shows the principal part structure of the cable core of the superconducting cable which concerns on embodiment of this invention. It is a graph which compares and shows the temperature characteristic of the critical current density (Jc) of a Bi-type superconducting tape wire and a Y-type superconducting thin film wire. It is sectional drawing of a Bi type superconducting tape wire. It is the structure explanatory drawing which fractured | ruptured the Y type superconducting thin film wire. It is a graph which shows the temperature characteristic of the critical current density (Jc) of a Y-type superconducting thin film wire and a Bi-type superconducting tape wire.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Former 2 Superconducting conductor layer 3 Insulating layer 4 Superconducting shield layer 11 Y system superconducting thin film wire 12 Metal substrate 13 Intermediate layer 14 Superconducting thin film 15 Protective layer 21 Bi system superconducting tape wire 21a Superconducting filament 21b Metal sheath

Claims (4)

A superconducting cable having a superconducting conductor layer and a superconducting shield layer formed on the outside through an insulating layer ,
A superconducting cable, wherein the superconducting conductor layer is formed of a layer of a Y-based superconducting thin film wire and a layer of a Bi-based superconducting tape wire .   The superconducting cable according to claim 1, wherein the Bi-based superconducting tape wire is disposed in a layer inside the superconducting conductor layer. A superconducting cable having a superconducting conductor layer and a superconducting shield layer formed on the outside through an insulating layer ,
A superconducting cable, wherein the superconducting shield layer is formed of a layer of a Y-based superconducting thin film wire and a layer of a Bi-based superconducting tape wire .   The superconducting cable according to claim 3, wherein the Bi-based superconducting tape wire is disposed in a layer outside the superconducting shield layer.

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